Various imaging media, most notably those which involve a photopolymerization reaction, require ultraviolet light for exposure. Examples of such media include printing plates, printed circuit boards, and 3M's Dynamark sign material.
Obtaining imagewise exposure of such media is costly and may require the services of a service bureau of another company which specializes in the use of appropriate imaging equipment.
Office printers have generally been viewed as unsuitable for preparing the images used in creating these signs, printing plates, or printed circuit boards.
Customary usage of ultraviolet-sensitive media is as follows. Computer data is prepared describing the desired image to be created. This data is then converted to raster format using a Raster Image Processor, or RIP, and sent to a laser imager. This imager, typically using a He-Ne laser, Argon ion laser, or laser diode, images onto silver halide film sensitive to the wavelength of the laser. The resultant film is black in regions where the final media is intended to be imaged. The film is then contact printed to obtain a wrong-reading, reversed image of the original film. The original film, when viewed facing the emulsion side, is readable. The contact print, when viewed facing the emulsion side, is wrong reading, i.e. lines of text read from right to left. Moreover, the areas to be imaged are white, rather than black. These reversals of image sense and color allow the contact print to then be placed in contact with the final media (e.g. sign material) and exposed in a contact printer using ultraviolet light. Following the exposure of this media, it is chemically processed to remove areas which were not exposed to the light.
It should be noted that the contact print (film to film) and the final imaging step (film to sign or other material) occur with the two media in pressurized contact with each other (e.g. in a vacuum frame contact printer) and includes emulsion to emulsion contact. Emulsion to emulsion imaging is desirable inasmuch as minimal spreading of the image occurs.
The original recording of the image onto silver halide film requires expensive equipment, this including not only the imager but also a chemical processor required for development of the film. A film recorder, such as the Linotype Linotronic L300.TM., costs about $50,000. A film processor may cost another $10,000, and may create various environmental problems. Companies which make signs often cannot afford such equipment, and/or may wish to avoid the environmental problems, and so must send floppy disks containing the image information out to a service bureau for preparation of films and negatives. After these are returned to the company making the sign, the contact exposure of the sign material is made. This process is both time-consuming and expensive.
Xerographic laser printers, e.g. the Hewlett-Packard Laserjet IIIP.TM., are usually capable of imaging the same information as is used by the service bureau. Such printers are usually less than 1/10 as expensive as the equipment used to create images onto film. If such printers could be used for creating signs, they could be made much more economically and quickly.